Add tabbed sub-views to bins section, create-bin-from-source flow

Bins section now mirrors the grids section with two tabs:
- Bins: gallery of processed bin records
- Sources: source images tagged with uses=['bin'], with upload and
  '+ Bin' button to create a bin record from an existing source image

Server: POST /api/bins/from-source accepts source_id, creates bin
record and adds 'bin' to the source image's uses array.

URL state: /bins → bins tab, /bins/sources → sources tab.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

public/templates.html

@@ -280,6 +280,7 @@
 			<div class="source-card-meta"></div>
 			<div class="source-card-uses"></div>
 		</div>
+		<button type="button" class="btn btn-secondary btn-sm source-card-create-bin" hidden>+ Bin</button>
 		<button type="button" class="btn-icon btn-danger source-card-delete" title="Delete">✕</button>
 	</div>
 </template>
@@ -592,12 +593,21 @@
 <template id="t-section-bins">
 	<section class="section" id="section-bins">
 		<div class="section-toolbar">
-			<label class="btn btn-primary">
-				<input type="file" id="bin-upload-input" accept="image/*" hidden>
-				+ Upload bin photo
+			<div class="tab-bar">
+				<button class="tab-btn" id="btn-tab-bins">Bins</button>
+				<button class="tab-btn" id="btn-tab-bin-sources">Source images</button>
+			</div>
+			<label class="btn btn-secondary" id="btn-upload-bin-sources" hidden>
+				+ Upload
+				<input type="file" accept="image/*" multiple hidden id="bin-source-upload-input">
 			</label>
 		</div>
-		<div class="bin-gallery" id="bin-gallery"></div>
+		<div id="tab-bins-content">
+			<div class="bin-gallery" id="bin-gallery"></div>
+		</div>
+		<div id="tab-bin-sources-content" hidden>
+			<div id="bin-source-image-list" class="source-gallery"></div>
+		</div>
 	</section>
 </template>